1. Field of the Invention
The present invention relates to a transmission image capturing technique.
2. Description of the Background Art
In medical fields, transmission images of a human body are captured by using X ray or the like. By reading the transmission images, diagnosis is conducted.
An X-ray diagnosing apparatus for so-called tomosynthesis is proposed, capable of observing a slice plane of a specimen at an arbitrary depth by synthesizing (reconstructing) a plurality of pieces of image data obtained by irradiating the specimen with X ray in different directions by image capturing using X ray.
At the time of capturing a plurality of projection images to generate an image of a slice plane, the position and angle of a scan system such as a part that emits radiation (for example, an X-ray tube) tend to be deviated from settings. Due to the deviation, so-called artifact such as distortion occurs in an image of a slice plane reconstructed. It is consequently very important to accurately grasp the position and angle of a part for generating radiation (radiation generating part) at the time of capturing a projection image.
To address such a problem, a technique of disposing a chart for calibration made of two microspheres, performing image capturing, and calibrating a scan system on the basis of the position of the chart for calibration in a projection image, thereby grasping the position and angle of a radiation generator more accurately and performing more accurate reconstruction has been proposed (for example, Japanese Unexamined Patent Application Publication No. 2003-61944).
However, in the technique proposed in Japanese Unexamined Patent Application Publication No. 2003-61944, calibration is performed in advance using the chart for calibration before image capturing. In the case where a different deviation occurs in the scan system at the time of image capturing, the position and angle of a radiation generator at the time of image capturing cannot be accurately grasped, and it is difficult to perform accurate reconstruction.